1. Technical Field
The present invention relates to a scintillator structure and a manufacturing method thereof, and more particularly, to a scintillator with sub-micron column structure and a manufacturing method for making the same, wherein the manufacturing method is used for making the scintillator with sub-micron column structure, and the scintillator with sub-micron column structure is able to transform the X-ray to a visible light for being applied in medical equipments, nuclear medicine, and security detection technologies.
2. Description of Related Art
Scintillator is a product of high-energy physics technology, which is used for transforming X-ray to an electronic signal or a visible light; therefore, the visible light transformed from X-ray can be further converted to an electronic signal by conventional optics device, for example, charge-coupled device (CCD). The scintillation occurring in the scintillator is a fluorescence induced by radiation. When a high-energy wave irradiates the scintillator, the ground state electrons in the scintillator would be excited and then migrate from ground state to excited state. Therefore, those excited electrons can further migrate to light-emitting excited state through non-light-emitting way, and then decay to lower energy state or base state for emitting photons (400˜1100 nm). Since crystalline scintillator includes high energy gap, the photons still cannot be effectively emitted although large electrons in conduction band migrate to valence band, or, the emitted photons cannot become visible light due to there high energy. Therefore, for increasing the emitting efficiency of visible light, a small amount of the activator is doped into crystalline scintillator for reducing the energy gap.
Because scintillator is able to transform X-ray to visible light, it is widely applied in medical equipments, nuclear medicine, and security detection technologies. Currently, Scintillators are divided into CsI scintillator, CsI(Na) scintillator and CsI(Tl) scintillator, wherein the CsI scintillator has been became the most conventionally used scintillator for its advantages of easy to be process, large size, sensitive to radiation, and high light-emitting efficiency. Generally, a good scintillator includes the following properties:    (1) transforming a radiation wave to a detectable light by high scintillation effect;    (2) linear transform;    (3) the production of the detectable light is proportional to energy of the radiation wave;    (4) including transparency and low self-radioactivity; and    (5) short light-decaying time.
Moreover, various application fields demand different requirements to the scintillators on incident radiation energy (keV), reaction time (ms), thickness (μm), area (cm2), and spatial resolution (1 p/mm), and these requirements are listed in following table 1.
TABLE 1crystalToothNon-destructivestructurologyMammographyImageinspectionAstronomyincident 8~2020~3050~7030~40030~600radiationenergy(keV)reaction<0.5<0.1<1<0.1<0.05time(ms)thickness30~50100~15070~120 70~1000 70~2000(μm)area30 × 3020 × 252.5 × 3.510 × 1030 × 30(cm2)spatial1015~207~105~104~5 resolution(lp/mm)
So that, according to above table, it can know that the incident radiation energy, the thickness and the spatial resolution will affect the light-outputting quality of the scintillator. Moreover, the signal to noise ratio (SNR) of scintillator increases with the incensement of the thickness thereof, and the SNR can be calculated by formula of SNR2=N0×[1−exp(−α×d)], where the No, α, d respectively present the incident photon number, incident energy, and thickness of scintillator.
In addition, anodic treatment is conventionally applied in surface corrosion resistance, painting, electrical insulation, electroplating, and wear resistance. The anodic oxide film made by anodic treatment usually includes porous structure, therefore a post sealing process must be applied to the anodic oxide film for facilitating the anodic oxide film become a dense membrane. Anodic treatment has the advantages of low cost and rapid production, and capable of being applied in producing large area products, such as dye-sensitized solar cells, thermal conductive sheets and thermal insulating components. Besides the anodic treatment, die casting process is also a low cost, rapid production technology.
On the other hand, traditional CsI scintillator process would cause some drawbacks in the CsI scintillator, for example, yellow discolouration, air pores, cloudiness, etc., and the yellow discolouration, the air pores and the cloudiness would impact the output of visible light and further reduce the efficiency of the CsI scintillator. In scintillator, the yellow discolouration is resulted from the combination of oxygen ions and thallium ions in the surface of scintillator, the air pores are caused by air or impurity remaining in the scintillator, and the cloudiness is an atomization induced by gathering of small oxygen bubbles.
According to the traditional CsI scintillator process includes many drawbacks, the semiconductor process technologies are used for manufacturing the scintillators, which includes the steps of: firstly, forming micron tube array on a silicon substrate by way of deep reactive ion etching (DRIE) or laser drilling, wherein the micron tube array is used as a waveguide film, and includes an aspect ratio of 20˜25 and a tube diameter of few microns. Next, vapor (or liquid) deposition is used for filling CsI material into the micron tube array, so as to complete a CsI scintillator. However, the mask, lithography, exposure, etching, and crystal growth equipments adopted in semiconductor process technology result in high manufacturing time and cost to CsI scintillator.
Accordingly, in view of the traditional CsI scintillator process and the semiconductor process technology for making CsI scintillator still have shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a scintillator with sub-micron column structure and a manufacturing method thereof, wherein the anodic treatment and the die casting technology having the advantages of low cost and rapid production are utilized for manufacturing a high-value scintillator with sub-micron column structure, and this scintillator with sub-micron column structure can also be applied in medical equipments, nuclear medicine, and security detection technologies.